Modern electrophotographic printers typically use some sort of processor to interpret a program representing the image to be printed. The program is written in some sort of graphical description language. The interpretation usually involves conversion of the program into machine executable instructions, such as a display list. These instructions are subsequently used to create a bitmap which determines a pattern of light that will expose a photosensitive drum. The exposure of the drum results in a charge pattern on the drum. The drum rotates past a toner dispenser and attracts toner particles to the drum's surface corresponding to the charge pattern. The drum transfers the toner to a print medium such as a piece of paper. The toner is fused to the paper, usually with heat, and the paper exits the printer.
The exposure unit that provides the pattern of light for exposing the drum can be comprised of a laser-scanning device or a spatial light modulator. Spatial light modulators are becoming the technology of choice for full color, high resolution printing at increasingly faster speeds.
As printer hardware improves, methods for providing faster image data processing are also needed. The number of pages printed per minute is highly dependent on the performance of the RIP (rasterized image processing).
U.S. Pat. No. 5,333,246, entitled "Page-Description Language Interpreter for a Parallel-Processing System", assigned to Seiko Epson Corporation, discusses using computers within a network to perform page description interpretation in parallel. However, this is a loosely coupled structure of processing devices, and communication among the processors is slow and complicated.